1. Field of the Invention
The present invention relates to a semiconductor device, and particularly to a power module on which power semiconductor elements are mounted.
2. Description of the Background Art
A semiconductor device called a power module, used for power control in an inverter or the like, on which are mounted a plurality of power semiconductor elements such as insulated gate bipolar transistors (IGBTs), power MOSFETs, or free wheel diodes (FWDs), is being widely used in the industrial field.
In general, a power module has a structure in which power semiconductor elements which convert power are mounted on an insulating circuit substrate in which a main circuit pattern is embedded, and mounted on a metal base plate for heat release, and furthermore, the outer periphery of the metal base plate is covered with a resin case.
Also, a semiconductor device called an intelligent power module (IPM), in which various kinds of control functions are added to the power module, incorporates therein an insulating circuit substrate for a main circuit, and in addition, a printed substrate having a control element and control circuit pattern.
In the IPM, a structure of two separate tiers of the insulating circuit substrate and printed substrate is generally adopted, and it is necessary to electrically connect the two substrates, the substrates and external terminals, and the like. Because of this, inside the device, an electrical connection is performed using metal plates called lead frames, bonding wires, any kind of soldering material, or the like, thus establishing a circuit necessary for the semiconductor device to function normally. Further, control signals supplied from the exterior of the IPM through control terminals are supplied to a control circuit in the IPM, thus driving the power semiconductor elements of the main circuit based on signals output from the control circuit, and it is thereby possible to carry out effective power control.
With regard to control signal internal wiring of the IPM, a technology described in JP-A-11-68035 and JP-A-2000-68446 is heretofore known. Details will be described hereafter.
FIG. 6 is a sectional view of a heretofore known IPM 100. An insulating circuit substrate 112 is placed on a metal base plate 111, and furthermore, power semiconductor elements 113 are placed on the insulating circuit substrate 112. A resin case 120 molded integrally with control terminals 130 and connecting terminals 131a and 131b is placed on the metal base plate 111 so as to surround the insulating circuit substrate 112.
The power semiconductor elements 113 are each furnished with main circuit wiring and control wiring using bonding wires or the like, and are connected to a printed substrate 150 using bonding wires 140 and the connecting terminals 131a and 131b as the control wiring, of the two wirings.
Furthermore, the control wiring between the printed substrate 150 and the exterior of the IPM is carried out using the U-shaped control terminals 130. The control terminals 130 are configured so as to be embedded in a case sidewall 120a. The inner portion of the IPM 100 is sealed with an insulating gel (not shown) or the like, and a cover 160 for foreign matter exclusion is placed on the upper portion of the IPM 100.
Next, a description will be given of a method of manufacturing the IPM 100. Firstly, the power semiconductor elements 113 are mounted on the insulating circuit substrate 112 using a solder or the like, and furthermore, mounted on the metal base plate 111 using a solder or the like.
Meanwhile, the control terminal 130 and connecting terminals 131a and 131b, each processed from a metal plate into a predetermined shape, are set in a mold tool, and insert molding is carried out, thereby forming the case 120. The molded case 120 is mounted using an adhesive or the like so as to surround the insulating circuit substrate 112 on the metal base plate 111. In this condition, the connecting terminals 131a and 131b and power semiconductor elements 113 are connected by the bonding wires 140.
A plan view at this stage is shown in FIG. 7, and a sectional view along the line VIII-VIII′ of FIG. 7 is shown in FIG. 8. As shown in FIG. 7, the connecting terminals 131a and 131b are provided on two respective opposite sides, of four peripheral sides of the case 120, and the control terminals 130 are provided on one side.
Subsequently, the printed substrate 150 is mounted so that the control terminals 130 and connecting terminals 131a and 131b are inserted into through holes provided in the printed substrate 150. Furthermore, by, for example, soldering the connections of the through holes and their respective terminals, the electrical connection between the printed substrate 150 and each terminal is secured, and the printed substrate 150 is fixed in the IPM 100.
Finally, the insulating gel (not shown) is injected into the inner portion, and the cover 160 is mounted using an adhesive or the like, thereby completing the IPM 100.
With regard to the main circuit wiring of the IPM 100, various kinds of wires are furnished with so as to be led out to the exterior of the IPM, in the same way as with the control wiring, but an illustration and description are omitted here.
However, as a result of an earnest investigation by the present inventor, it is revealed that the IPM of the heretofore known structure has various problems. Details will be described hereafter.
An IPM is eventually used by being incorporated inside each kind of device necessary for power control, but when the area used exclusively by the IPM is large, a device in which the IPM is incorporated also increases in size, meaning that a further reduction in the size of the IPM has been strongly demanded in recent years. Meanwhile, the case sidewall 120a has to hold the control terminals 130 using insert molding, and it is not possible to make the thickness of the case side wall 120a smaller than a thickness enough to be able to hold the control terminals 130. Also, as the control terminals 130 are disposed on the case sidewall 120a, as shown in FIG. 6, wiring extending in a horizontal direction from the printed substrate 150 is necessary, but it is also necessary to secure a space for this extension wiring. It has thus been revealed that the necessity of the sidewall thickness and horizontal wiring prevents a reduction in the area used exclusively by the IPM.
Furthermore, as there exists no standard relating to positions on the IPM in which the control terminals are mounted, it is necessary to mount the control terminals 130 indifferent positions required depending on use applications. Meanwhile, as the control terminals 130 are mounted on the case 120 by insert molding, as previously described, it is necessary to prepare various kinds of insert molding tools corresponding to the different mounting positions of the control terminals 130. In this way, the necessity of preparing various kinds of mold tools leads to an increase in the manufacturing cost of the IPM.